Stocks were under pressure as Wall Street worried that the unexpected increase in the PPI would dissuade the Federal Reserve from instituting rate cuts that the slipping market has used as harbingers of hope.

its board authorized a $15 billion share buyback

In active retail earnings news, Home Depot fell short of analyst estimates and warning of difficult times ahead. The home improvement giant said earnings per share could fall as much as 24 percent this year, and it scaled back plans for new store openings. Its shares, though, posted only modest losses.

Radio Shack, meanwhile, saw shares soar after it reported a 19.5 percent increase in fourth-quarter profit that beat analyst estimates. The electronics retailer led gainers on the S&P.

Among companies reporting before the bell, Target posted profitof $1.23 a share that, though sharply lower from 2007, narrowly beat expectations. Macy'sbeat analyst estimateswith a profit of $1.65 a share, and Office Depot badly missed expectations, with its profit tumbling to 7 cents a share against projections of 18 cents.

Technology stocks showed early strength, even briefly sending the Nasdaq into positive territory, but fell as leaders Google and Apple continued to see their shares pummeled.

Meanwhile, MBIA, the world's largest bond insurer, said Monday it was eliminating its quarterly dividend in a move expected to save the company $174 million a year.

The company also said it would stop ensuring new derivative credit contracts, and suspended the writing of new structured finance business for the next six months.

Investors will also watch earnings reports from retailers.

And foreclosure filings rose 8 percent in January from December and increased nearly 57 percent from January 2007, showing that foreclosure activity continues its upward trend, a RealtyTrack report showed.